The effects of invasive species on native ecosystems are varied, and these have been linked to the disappearance or decline of native fauna, changes in community structure, modification of ecosystems and as vectors of new diseases and parasites. Besides, the development of trade in species for ornamental use has contributed significantly to the import and introduction of invasive fish in some important areas for biodiversity conservation in Mexico, but the presence of these species is poorly documented. In this study we analyzed the fish community in the Biosphere Reserve Sierra de Huautla by looking at diversity changes in the last 100 years. For this, we used databases of historical records and recent collections for five sites in the Amacuzac river, along the Biosphere Reserve area. We compared the values of similarity (Jaccard index) between five times series (1898-1901, 1945-1953, 1971-1980, 1994-1995 and 2008-2009), and we obtained values of similarity (Bray-Curtis) between the five sites analyzed. In our results we recognized a total of 19 species for the area, nine non-native and ten native, three of which were eliminated for the area. Similarity values between the early days and current records were very low (.27); the major changes in the composition of the fauna occurred in the past 20 years. The values of abundance, diversity and similarity among the sampling sites, indicate the dominance of non-native species. We discuss the role of the ornamental fish trade in the region as the leading cause of invasive introduction in the ecosystem and the possible negative effects that at least four non-native species have had on native fauna and the ecosystem (Oreochromis mossambicus, Amatitlania nigrofasciata, Pterygoplichthys disjunctivus and P pardalis). There is an urgent need of programs for registration, control and eradication of invasive species in the Sierra de Huautla Biosphere Reserve and biodiversity protection areas in Mexico.